One of the most difficult problems when making deliveries with a truck is loading and unloading the truck. Some locations have loading docks at the same height as the truck bed to facilitate loading and unloading. Such locations support fast loading, stacking and unloading of cargo being carried on the truck by using pallet jacks, lift trucks and other cargo handling equipment.
Properly configured loading docks are highly useful and efficient. But not all locations have such docks. Almost all local deliveries and cargo pickups are performed at ground level. This leaves a gap of several feet from moving cargo from the truck bed to ground or from the ground to the truck bed. In some particular applications it has been found useful to simply carry a lift truck on the back of the cargo truck to assist loading and unloading cargo. Unfortunately this involves a significant amount of money, difficulty in using the lift truck, difficulty in carrying the lift truck so that is can be rapidly positioned at ground level, and it can be dangerous. Furthermore such an approach is useless at some locations where the ground is less than ideal or in operations not suitable for carried lift trucks.
One solution to the problem of loading and unloading cargo onto and from trucks is the use of hydraulically powered tail gates (also referred to as lift gates). Such tail gates are platforms that are attached to the back of the truck and which can hydraulically raise or lower a load to and from ground onto and from the truck bed. Tail gates have proven themselves as highly valuable devices that greatly ease the difficulty of loading and unloading trucks.
While tail gates are widely used they are not without problems. One serious problem with prior art tail gates is that they require wired electrical switches to operate and control the hydraulic pump unit that actually moves the tail gate. For convenience at least some of those wires and electrical switches are located proximate the tail gate itself. Given the rugged conditions that exist in moving cargo it is not surprising that damage to the wiring or electrical switches is very common. Such damage can be costly and time consuming to repair while resulting in some cargo not being loaded or unloaded until the damage is fixed.
In view of the problems with prior art hydraulic tail gates a hydraulic tail gate system having increased reliability would be beneficial. Beneficially such a hydraulic tail gate system would enable simplification of the electrical system required for its operation. In practice such a hydraulic tail gate system would be particularly useful if it eliminated the need for expensive high current switches and wires. Preferably such a hydraulic tail gate system could be incorporation into new trucks or implemented as a retrofit kit for existing hydraulic tail gates. Such a hydraulic tail gate system would be even better if it implemented a sensor system for checking system status and failure diagnostics.